James Silvey, RSPB Scotland Nature Recovery Officer, tells us about a recent attempt to find a sun-seeking butterfly.
In search of the mountain ringlet
Mountain ringlet by Oliver Smart (rspb-images.com).
“It could be there, you just never know till you look”. That’s what I found myself telling the group of eager volunteers who had donated their time to searching for the elusive mountain ringlet butterfly on the slopes of Beinn a’ Choin, at our Inversnaid reserve on a beautiful sunny day in July.
The mountain ringlet Erebia epiphron is a peculiar insect and our only truly montane butterfly species. Try as hard as you like, you will not find this butterfly lower than 400m but it has been recorded as high as 900m. Superficially the butterfly looks like its close relative the Scotch argus Erebia aethiops but its habits couldn’t be more different.
Apart from living where most butterflies would fear to tread, the mountain ringlet is also a real sun worshipper. Unless there is bright sunshine during its short 2-4 weeks flying period the mountain ringlet refuses to fly. Even a passing cloud will see individuals charging down into the grass, awaiting the next wave of sunlight before returning to their slow flight over the vegetation.
The nearest population to Inversnaid is found on the southern slopes of Ben Lomond, 7km away as the butterfly flies. As far as we know this population is the most southerly in Scotland and one of the most isolated.
Mountain ringlets are present on Haweswater reserve in the Lake District but as yet no populations have been found on any of RSPB Scotland reserves, which sounded like a challenge.
Looking at maps and aerial photos Inversnaid looked well suited. Wet gullies looked to harbour large patches of mat-grass (the caterpillar’s only food plant) and southerly slopes would provide plenty of basking locations for the adults. Standing in the car park in the baking sunshine it looked even better.
Our destination was a 2hr climb to the start of the survey site at 500m with a further 2hr climb to the end and summit at 770m.
Along the survey route the habitat looked fantastic, mat-grass dominating the wet gullies and tormentil and wild thyme providing perfect nectaring sites for the adults. Everything looked ideal apart from the lack of mountain ringlets.
Intrepid volunteers at the summit.
Other butterflies and moths (including a couple of beautiful wood tigers) were seen in good numbers but it seemed the mountain ringlet was absent from the site. It was hard to be disappointed though especially when we reached the summit of Beinn a’ Choin with the sun shining, overlooking Loch Lomond and with countless new records of other species for the reserve.
On the walk back down and with Ben Lomond and its population of mountain ringlets looming in the distance, I couldn’t help but think the future still looked positive. Grazing on the reserve has been hugely reduced since RSPB began management of the site allowing a variety of montane plants to flourish. It seems the area is primed and ready for an enterprising female to take the daring flight over from Ben Lomond and begin the colonisation process.
It feel like time is all we need and Inversnaid has plenty of that.
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